Levels of unintended fertility in the United States are high: half of all pregnancies and a third of all births are unintended, with higher levels among young adults and among race-ethnic-nativity minorities. Because unintended births are associated with negative health outcomes, higher rates of unintended fertility among minorities may exacerbate health disparities, and reducing unintended fertility has been a public health goal since the 1980s. Although the proximate determinants of unintended fertility are clear (sex without effective contraceptive use and carrying unintended pregnancies to term), the underlying causes of these behaviors, and of race-ethnic-nativity differences, are not well understood. Drawing on existing frameworks for understanding fertility differentials, this project proposes two key distal determinants - reproductive knowledge and fertility motivation - that may explain differences in unintended fertility across race-ethnic-nativity groups. The project wil test the hypotheses that race-ethnic-nativity minorities have lower reproductive knowledge and motivation to prevent pregnancy; that these differences widen during young adulthood; and that these distal determinants drive differences in the proximate determinants (primarily sex and contraception) and in fertility itself. This project moves beyond prior descriptive work to identif precursors of risky sexual behavior and unintended fertility during young adulthood, a life course stage that is highly variable yet understudied in the fertility literature. We also extend prior wok by incorporating both men and women as well as diverse race- ethnic-nativity groups. Our project will derive robust and consistent measures from three complementary datasets: the Relationship Dynamics and Social Life study (RDSL; a population-based sample of women aged 18-19 residing in a Michigan county in 2008/09, followed weekly for 2.5 years), the National Longitudinal Study of Adolescent Health (Add Health; youths enrolled in grades 7-12 in 1995 and reinterviewed in 1996, 2001/02, and 2007/08), and the 2009 National Survey of Reproductive and Contraceptive Knowledge (Fog Zone; a national sample of unmarried men and women aged 18-29). First, the project will create equivalent measures of the distal determinants across surveys and race-ethnicity-nativity, using factor and latent class analyses guided by integrative data analysis techniques. Second, cross-lag regression models will be used to examine the stability of these constructs as young adults learn and gain new experiences that may affect their reproductive knowledge and fertility motivation. Third, this work will use event history models to identify the elements of fertility motivation and reproductiv health knowledge that are most predictive of risky sexual behavior and unintended births. Findings will guide future research and interventions in targeting those at risk for unintended fertility and highlighting the most crucial domains for intervention. To disseminate our findings t policymakers and practitioners, we will work with a consultant from the National Campaign to Prevent Teen and Unplanned Pregnancy, a nationally respected, politically neutral, private advocacy organization.